Survey Sampling (ECON1320 – L10)

Survey Sampling (ECON1320 – L10)

Terms

1. Element: an object on which a measurement is take

2. Population: a collection of elements about which we wish to make an inference

3. Sampling units: non-overlapping collection of elements in the population

4. Sampling frame: a list of sampling units

5. Sample: a collection of sampling units drawn from a frame or frames

6. Efficient: an unbiased estimator is said to efficient if it has a lower variance than any other unbiased estimator. Such an estimator will, on average, yield smaller standard errors and narrower confidence intervals for a given sample size.

Errors in Survey Sampling

Non-sampling Errors

1. A faulty sampling frame (due to incomplete, out-of-date or otherwise unrepresentative)

2. Non-response (can maximize the response rate with a good questionnaire design, publicity well in advance, industry sponsorship, assurances of confidentiality, incentives)

3. Response and recording errors (due to errors in questionnaire design – ambiguous question, expectation errors – when answers to questions early in the interview condition the interviewer to expect particular responses to subsequent question, the manner of asking the question – when the interviewer is forced to deviate from the wording on the questionnaire)

4. Errors in the processing of data

Sampling Errors

- Is the difference between a sample statistic and the corresponding population parameter that occurs even with a random sample and a well-designed survey

- Is unavoidable consequence of being able to observe only a subset of the element in the population

- Is recognized in the statistical formula (e.g. a CI estimation = sample statistic +/- sampling error)

- Can be reduced by

o Increasing the sample size, and

o Using a different sampling method

Alternative Sampling Designs

Non –random samples

1. E.g. self selection surveys – invariably yield biased results.

Random samples:

1. Simple random sampling

a. SRS with replacement

b. SRS without replacement

2. Stratified random sampling

3. Cluster sampling

4. Systematic sampling

5. Randomized Response sampling

TBC…